1. Field of the Invention
The present invention relates to a method of manufacturing a semiconductor device for fabricating a cylindrical capacitor and the like.
2. Description of the Related Art
Currently, in memories such as DRAM (Dynamic Random Access Memory), a capacitor is used as a device for storing information. The occupied area of the capacitor in each memory cell of the memory has reduced in accordance with high integration of semiconductor integrated circuits. As a result, capacitance of a capacitor is decreased. However, for the capacitor to sufficiently function as a memory cell, it is necessary to ensure constant capacitance. Also, in order to obtain a sufficient margin for soft errors or noises due to alpha (xcex1) ray emitted from the package and cover which accommodate the memory, it is necessary to further increase the capacitance. Therefore, in order to increase the capacitance of capacitors, a method of using a ferroelectric film with high permittivity, a method of increasing the electrode area of capacitors, and the like are proposed.
One of the methods of increasing the electrode area of the capacitor employs an HSG (Hemispherical Grain) film for electrodes (disclosed in for example, Japanese Patent Application Laid-open Hei 8-306646). In the method, first, silane (SiH4) is irradiated (supplied) to an amorphous silicon film, which is an amorphous semiconductor film containing an impurity, used for a bottom electrode of a capacitor to form crystal nuclei on the surface thereof. Then, annealing is performed so that the silicon atoms on the surface of the amorphous silicon film are migrated towards the formed crystal nuclei. Thereby, HSG-Si (Hemispherical Grained Silicon) is formed on the surface of the amorphous silicon film. After forming the HSG film as described, annealing is performed in, for example, phosphine (PH3) atmosphere in order to suppress depletion. As a result, phosphorus (P), which is an impurity, is diffused to the hemispherical grain, thereby forming the bottom electrode of a capacitor. Then, a dielectric film (for example, a nitride film) and a top electrode are formed in order for fabricating a capacitor.
In the above-described method of the related art, a phosphorus compound, which is a phosphorus product generated by annealing in PH3 atmosphere, is attached to the silicon film. Therefore, cleaning is performed for removing the phosphorus compound through etching using SC1 (a mixed solution of ammonium hydroxide (NH4OH) and hydrogen peroxide (H2O2)) as a cleaning solution. Then, in order to remove native oxide and the like, cleaning is performed through etching using dilute hydrofluoric acid (DHF). However, when SC1 is used, the hemispherical grains come off by etching. This results in the decrease of the electrode area and short circuit in the bottom electrodes of the adjacent capacitors. In the case where cleaning is performed using dilute hydrofluoric acid instead of using SC1 in order to avoid these problems, a cleaning tank of hydrofluoric acid is contaminated by the phosphorus compound.
The invention has been designed to overcome the foregoing problems. An object of the invention is to provide a method of manufacturing a semiconductor device capable of effectively removing impurity products attached to a semiconductor film while suppressing coming off of, for example, hemispherical grains as much as possible formed on the semiconductor film containing an impurity.
A method of manufacturing a semiconductor device of the invention comprises the steps of: forming a semiconductor film on a substrate and then growing spherical or hemispherical grains on the surface of the semiconductor film; diffusing an impurity to the grains grown on the surface of the semiconductor film; and removing the impurity product, which is generated in the step of diffusing the impurity, from the surface of the semiconductor film using hot water.
Another method of manufacturing a semiconductor device of the invention comprises the steps of: forming a semiconductor film on a substrate and then growing spherical or hemispherical grains on the surface of the semiconductor film; diffusing an impurity to the grains grown on the surface of the semiconductor film; and removing the impurity product, which is generated in the step of diffusing the impurity, from the surface of the semiconductor film using either a mixed solution of hydrochloric acid and hydrogen peroxide or a mixed solution of sulfuric acid and hydrogen peroxide.
In a method of manufacturing a semiconductor device of the invention, spherical or hemispherical grains are formed on the surface of a semiconductor device on a substrate. Then, an impurity is diffused to the grains grown on the surface of the semiconductor film. The impurity product, which is generated in the step of diffusing the impurity, is removed from the surface of the semiconductor film using either hot water, a mixed solution of hydrochloric acid and hydrogen peroxide or a mixed solution of sulfuric acid and hydrogen peroxide.
Other and further objects, features and advantages of the invention will appear more fully from the following description.